As 2008 draws nearer, so does the temporary impulse of pious optimism that men call the New Year resolution. While pondering the shamefully wide range of behavioural modifications that might make us better citizens of the world, we might listen to Sir Paul McCartney, who has been prosyletising about a subject close to his heart. "To me, there's nothing more exciting than changing your opinion on something," he says; and he wants to change the majority of the population's opinion about food. Inspired by a recent United Nations report that livestock farming uses almost a third of the world's land surface, Sir Paul recommends that we all simply stop eating meat. The report, he says, "contains one clear message: the single most effective act that any individual can do to lessen the effects of global warming is to become vegetarian."

He is, of course, right to express concern that raising cattle on the great plains of the world affects the rainforest, and increases emissions of dubious gases. But the former Beatle (and president of the Vegetarian Society of Great Britain) overstates his case. To imagine that ceasing to eat animals would have any effect on the fallout from global warming is to live in a cloud cuckoo land not unlike that expressed in John Lennon's "Imagine," when he sang "Imagine no possessions... It isn't hard to do... Nothing to kill or die for... And no religion too", seated at his expensive piano.

It's always pleasant to encounter vestigial traces of the Sixties spirit. But perhaps it comes across better in a song lyric than a serious argument.